Color crt having shadow mask with forwardly directed, outwardly flared skirt

ABSTRACT

This disclosure depicts a color cathode ray tube having supported on the envelope thereof a novel light-weight, low cost shadow mask with provisions for electron shielding and mask rigidification. The mask includes a forwardly directed, outwardly flared skirt which shields a phosphor screen on the tube faceplate from stray and overscanned electrons. The skirt includes novel structure for imparting a predetermined rigidity characteristic to the mask. The mask is supported on the envelope of the tube by four mask suspension devices located at the corners of the mask.

' United States Patent [191 Sedivy 1 Oct. 14, 1975 COLOR CRT HAVING SHADOW MASK WITH FORWARDLY DIRECTED, OUTWARDLY FLARED SKIRT [75] Inventor: Stanley J. Sedivy, Chicago Ridge,

Ill.

[73] Assignee: Zenith Radio Corporation, Chicago,

Ill.

[22] Filed: Sept. 7, 1973 21 Appl. No.: 395,334

[52] us. Cl 313/402; 313/408 [51] Int. Cl. H01J 29/80 [58] Field Of Search 313/85 S, 402, 403, 407, 3 1 3/ 408 [56] References Cited UNITED STATES PATENTS 2,961,560 11/1960 Fyler 313/85 S X 3,404,302 10/1968 Nicklas 313/85 S 3,479,546 1 H1969 Mears 313/85 S 3,548,235 12/1970 Driedijk et al... 313/85 3,558,955 1/1971 Kirchner 313/85 5 3,700,949 10/1972 Watanabe 313/85 S 3,703,655 ll/l972 Kawamu'ra 313/85 S FOREIGN PATENTS OR APPLICATIONS 32,495 7/1967 Japan Primary EtaminerAlfred E. Smith Assistant Examiner-Rolf Hille Attorney, Agent, or Firm-John H. COult ABSTRACT This disclosure depicts a color cathode ray tube having supported on the envelope thereof a novel lightweight, low cost shadow mask with provisions for electron shielding and mask rigidification. The mask includes a forwardly directed, outwardly flared skirt which shields a phosphor screen on the tube faceplate from stray and Overscanned electrons. The skirt includes novel structure for imparting a predetermined rigidity characteristic to'the mask. The mask is supported on the envelope of the tube by four mask suspension devices located at the comers of the mask.

14 Claims, 6 Drawing Figures U.S. Patent bct.14,1975 Sheet10f3 3,912,963

U.S. Patent Oct. 14, 1975 Sheet 2 of3 3,912,963

8 V N QNBQ US. Patent Oct. 14, 1975 Sheet 3 of3 3,912,963

FIG. 5

COLOR CRT HAVING SHADOW MASK WITH FORWARDLY DIRECTED, OUTWARDLY FLARED SKIRT CROSSREFERENCE TO RELATED APPLICATION This application relates to, but is in no way dependent upon, copending application Ser. No. 535,475, filed Dec. 23, 1974 (a continuation-in-part of nowabandoned application (Ser. No. 395,106, filed Sept. 7, 1973), Ser. Nos. 424,017 and 424,018, both filed Dec. 12, 1973, and Ser. No. 498,836, filed Aug. 19, 1974 (a continuation of now-abandoned application Ser. No. 285,985, filed Sept. 5, 1972,) all assigned to the assignee of the present invention.

BACKGROUND OF THE INVENTION This invention relates to shadow mask-type color cathode ray tubes and especially to an improved shadow mask. The shadow mask of this invention has general applicability but is especially suited for use in a novel color cathode ray tube having an envelope assembly which includes a flangeless front panel or faceplate. The mask is of a light-weight, preferably frameless, torsionally flexible construction which is adapted to be supported at its corners such that it assumes the contour of the faceplate.

Conventional shadow masks are relatively heavy, rigid structures, typically comprising a rigid frame to which is attached a perforate mask formed to the same configuration as the tube faceplate. Conventional color cathode ray tubes have an envelope comprising a funnel which is sealed to a front panel. The front panel has a window or faceplate portion surrounded by a rearwardly extending flange. The conventional mask assembly is suspended within the panel by a plurality of springs attached to the mask at spaced points around the periphery thereof which engage studs extending inwardly from the panel flange.

The novel cathode ray tube mentioned above with which the shadow mask of this invention is most advantageously associated is designed for minimized cost of manufacture and, to this end, employs a faceplate which does not have a flange from which a shadow mask may be suspended. Further, the type of mask suspension devices used to support such prior art masks are unsuitable for mounting a mask directly on the faceplate of a tube. Also, the high cost of manufacture of prior art shadow mask assemblies, due in part also to the need for a separate electron shield assembly, renders them unacceptable for use in this low cost tube.

OBJECTS OF THE INVENTION It is a general object of this invention to provide an improved shadow mask for a color cathode ray tube.

It is a less general object to provide a low cost shadow mask for use in a color cathode ray tube having a flangeless faceplate.

It is still another object to provide an improved shadow mask which is of one-piece construction, which performs an electron shielding function and which has substantial rigidity about major and minor axes of the mask, while being light-weight and deliberately flexible in torsion.

It is yet another object to provide a mask which may be mounted directly upon the faceplate of a color cathode ray tube by the use of mask suspension devices which are relatively short and thus not prone to into- PRIOR ART United States 3,521,104 Mears 3,529,199 Duistermaat et al 3,548,235 Driedijk et a1 3,558,955 Kirchner 3,700,949 Watanabe et all 2,824,989 Christofferson 2,942,129 May 2,961,560 Fyler 3,404,302 Nicklas 3,479,546 Mears British BRIEF DESCRIPTION OF THE DRAWINGS The features of the invention which are believed to be novel are set forth with particularity in the appended claims. The invention, together with further objects and advantages thereof, may best be understood, however, by reference to the following description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a rear perspective view of a color cathode ray tube with a portion of the envelope cut away to reveal a novel shadow mask implementing the principles of this invention;

FIG. 2 is an elevational view of the FIG. 1 tube, partially sectioned and showing particularly the shadow mask and its suspension system;

FIG. 3 is a plan view of one of the mask suspension devices illustrated in FIGS. 1 and 2;

FIGS. 4 and 5 are sectional views taken along lines 4-4 and 55 in FIG. 1; and

FIG. 6 is a fragmentary view of a mask according to this invention, supported by the flange of a conventional color cathode ray tube front panel.

The drawings illustrate a color cathode ray tube embodying a shadow mask implementing the principles of this invention. As noted above, the shadow mask principles of this invention have general applicability but are of particular significance as applied to a novel color tube 10 having an envelope comprising a funnel 12 to which is bonded a skirtless front panel or faceplate 14. The tube includes a shadow mask 16 constructed to implement the teachings of this invention; the shadow mask 16 will be described in detail after structure associated with the shadow mask has been described.

The mask 16 is illustrated as being supported directly on the faceplate 14 by a mask suspension system comprising four mask suspension devices 18, one located at each corner of the mask, which permit the mask to be quickly and precisely mounted within the tube. The illustrated mask suspension system constitutes another of my inventions which is described in detail and claimed in the referent copending applications Ser. No. 535,475 and Ser. No. 424,017.

The general concept of a flexible mask which is supported at its corners so as to permit it to conform to the contour of a cathode ray tube faceplate is described and claimed in the referent copending application Ser. No. 498,836. The illustrated mask suspension devices 18 each comprise mask-mounted means and faceplatemounted means which are structured and arranged such they mate with a snap-in, self-guiding and self-locating engagement. In FIGS.'1-5=the maskmounted means is depicted: as comprising a leaf spring 20 which carries convergent lug means in the form of a conically tapered lug 22. The leaf spring 20 is supported on a bimetal member 23 which is affixed at a corner of the mask 16 by a pair of arms 24, 26. The arms 24, 26 bridge the. corner of the mask and are welded thereto on opposite sides of the corner.

The bimetal member 23 and the functions it performs are described and claimed in the referent copending application Ser. No. 424.018. Briefly, the bimetal member 23 comprises two edge-bonded strips of metal having different coefficients of thermal expansion. The member 23 deflects, when heated, in its own plane. The member 23 is caused to assume an angle relative to the faceplate14 which is such that the member will have a component of flexure which is effective to relieve stresses in the mask 16 introduced by thermal expansion of the mask.

In the illustrated embodiment, the panel-mounted means is shown as comprising a stud 32 secured to the faceplate 14. The stud 32 may be embedded in the faceplate 14 in a manner well known in the art, or bonded thereto. The stud 32 integrally defines a tapered guide channel 34 for receiving the lug 22 carried by the leaf spring 20 during a mask insertion operation. The guide channel 34 directs the lug 22 into snap-in, self-locating engagement in an opening 36 constituting ase'at for the lug 22.

To mount the mask 16 in the tube 10, the operator, or an automated mask-inserting instrumentality, merely orients the mask to correspond to the orientation of the faceplate l4 and translates the mask along the t'ubeaxis until the lugs 22 engage the guide channels 34 in the studs 32. Upon the application of a force on the mask in the direction of the tube axis, the springs deflect back and permit the lugs 22 to follow the guide channels 34 into snap-in engagement with the openings 36.

As pointed out in detail in the referent application Se'r. No; 498,836 in a mask suspension system according to the invention mask suspension devices are provided at the four corners of the mask, however only three of the four mask suspension devices locate the maskin X, Y and Z coordinates. Assuming the tube axis to represent the Z axis, all four of the devices locate the mask in the Z coordinate, whereas only three of the four devices fix the position of the mask in the X and Y coordinates. To this end, one of the mask suspension device's, shown at the upper-right mask corner in FIG. 1, has a guide channel 34 and opening 36 which are elo'ngated parallel to the faceplate 14 to permit the maskto float in the X-Y plane while fixing its spacing from the faceplate l4.

'This invention is directed to the provision of a low cost shadow mask which is capable of being mounted upon the flange of a conventional color cathode ray tube front panel or directly upon the faceplate of a cathode ray tube and which has novel provisionfor electron shielding and mask rigidification. The shadow mask 16 illustrated in FIGS. l-S represents but one of many possible implementations of the principles of this invention. The mask 16 is depicted ascomprising a sheet of electrically conductive material, such as steel,

having a curved central portion 38 which has formed therein a pattern of electron-transmissive apertures 40.

The mask includes a strengthening channel 42 formed iht'egrally in the sheet which extends rearwardly into the tube such that its concave surfacefaces toward the faceplate 14. The primary function of the channel 42 is to enhance the rigidity of the shadow mask about major and minor axes, HH and VV. The particular orientation and configuration of the channel is, however, designed to serve an electron shielding function, as described in more detail below.

The mask 16 has an integral skirt 44 surrounding the strengthening channel 42. The skirt 44 includes a forwardly directed, outwardly flared body portion 46 which terminates in a leading edge portion 48. The flare angle 0 of the body portion 46 of the skirt 44 is selected to correspond generally to the maximum scan angle of the electron beams (see FIG. .4). The flare angle 0 of the body portion 46 of the skirt 44, the configuration of the leading edge portion 48, and the crosss'ectional configuration of the strengthening channel 42 areselected so as to accomplish a shielding of the phosphor screen 50 on the inner surface of the faceplate 14 from stray or overscanned electrons from the electron beams 49. FIG. 4 illustrates with ray diagrams a'number of overscanned electron beam trajectories. It is clear from an inspection of these ray diagrams that effective shielding of the phosphor screen 50 from stray or overscanned electrons is accomplished by the novel channel 42and skirt 44. v 1 Q As mentioned briefly above, his desirable that the mask 16 have torsional flexibility about the mask diagonals in order to permit it to conform to the contour of the faceplate 14. It is also desirable, however, that the mask be rigid about the major and minor mask axes, Hl-l and VV. As described above, thestrengthening channel 42 provides a substantial degree 'of mask rigidiflcation about the major and minor mask axes. Further to this end, it is desirable that'the Skin 44 further contribute to the rigidity of the mask about its major and minor axes. I v i In accordance with one aspect of this invention there is provided integrally formed in the body portion 46 of the skirt a plurality of novel rib elements 54 along each side of the mask. The rib elements 54 on each side of the mask are individually straight and mutually paralle and are approximately orthogonal to the tube axis; The rib elements 54 are successively offset laterally and arranged such that as a group they follow the contour of the mask central portion 38. At least the end portions of the elements 54 are disposed side-by-side. Iridividuaily, the rib elements 54 are arranged as sections of chords of the curved contour of the skirt 44. The rib elements 54 are effective to substantially synthesize a load-bearing beam having an effective load-bearing depth which is greater than the depth of any rib element but which is less than the overall depth of the skirt. It is within the purview of this invention to use rib elements in other numbers and of other individual and relative lengths and depths consistent with the abovestated specifications.

As described above, the flared, forwardly directed skirt on the mask'serves as an electron shield the skirt also serves an additional important'function. By being flared outwardly and directed forwardly, the skirt 44 provides structure for supporting a component of a mask suspension device 18. Because the skirt 44 lies closely adjacent to the faceplate, the device 18 may be relatively short, thus minimizing the likelihood that errors in mask positioning may be introduced during the tube manufacturing operations or during operation of the tube.

In the above-described embodiment the shadow mask of this invention has been illustrated as being mounted by the use of a mask suspension system especially adapted for supporting a mask directly upon the faceplate of a color cathode ray tube. As stated above; however, a shadow mask according to this invention is adaptable to being mounted in various ways on various parts of a color cathode ray tube envelope, including the flange of a conventional flanged cathode ray tube front panel.

FIG. 6 is a fragmentary view of a shadow mask 102 according to the invention corner mounted on a flanged front panel 103 by four suspension devices 104 (only one of which is shown). The device 104 is illustrated as comprising mask-mounted means somewhat similar to the mask-mounted means shown in the FIGS. 1-5 embodiment. The mask-mounted means comprises a leaf spring 106 having a tip portion 108 which is formed concave outwardly so as to define a guide channel functioning as does the guide channel 34 in the FIGS. l5 embodiment.

The tip portion 108 has formed therein an aperture 110 adapted to engage a conical tip 112 on a lug 114 embedded or otherwise affixed to the flange 116 of the front panel 103. The FIG. 6 embodiment functions in substantially the same manner as the afore-described embodiments. To mount mask 102 in the front panel 103, the mask-mounted means and the lug 114 are aligned and the mask is then translated along the tube axis. The mask-mounted means and the lug 114 mate with a snap-in, self-guiding, self-locating engagement to accurately mount the mask in the tube at a predetermined distance from the faceplate 118 of the front panel 103.

The invention is not limited to the particular details of construction of embodiments depicted and other modifications and applications are contemplated. For example, the shadow mask may have configurations other than as shown which are consistent with the teachings of this invention. The provision of a strengthening channel may be avoided if sufficient rigidity is otherwise imparted to the mask. Other configurations of the strengthening channel and skirt may be devised in accordance with this invention. Certain other changes may be made in the above-described apparatus without departing from the true spirit and scope of the invention herein involved and it is intended that the subject matter in the above depiction shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. For use in a rectangular color cathode ray tube having a faceplate carrying phosphor screen, a generally rectangular, frameless shadow mask having a perforate curved central portion with its convex surface facing forwardly toward the faceplate when the mask is operatively mounted in the tube, and a forwardly directed skirt surrounding said central portion and flared outwardly at an angle corresponding substantially to the angle of maximum electron beam deflection, said skirt functioning to shield the screen from stray elec trons and to impart rigidity to the mask.

2. The mask defined by claim 1 wherein said skirt is of substantially constant depth around said central portion and has a curved contour following the curvature of said central portion of the mask, and wherein said skirt has formed integrally therein discrete raised ribs extending along the skirt for imparting strength to the mask.

3. The mask defined by claim 2 wherein said strengthening rib comprise rib elements extending lengthwise along at least the opposed long sides of said mask, said rib elements being straight, mutually parallel and successively offset laterally with end portions thereof being disposed side-by-side, said rib elements being arranged as sections of chords of said curved contour of the skirt which are oriented orthogonal to the central axis of the tube so as to substantially synthesize a load-bearing beam having an effective loadbearing depth which is greater than the depth of any individual rib element but less than the overall depth of the skirt.

4. For use in a rectangular color cathode ray tube having a faceplate carrying a phosphor screen, a generally rectangular shadow mask formed as a unitary structure from a sheet of electrically conductive metal and having as integral parts thereof a perforate curved central portion with its convex surface facing forwardly toward the faceplate when the mask is operatively mounted in the tube, a channel portion surrounding said central portion for strengthening the mask, and a forwardly directed, outwardly flared skirt surrounding said channel portion which functions as an external shield and which imparts rigidity to the mask.

5. The mask defined by claim '4 wherein said skirt is of substantially constant depth around the mask and has a curved contour following the contour of said central portion of the mask, and wherein said skirt has formed integrally therein strengthing rib elements extending lengthwise along at least the opposed long sides of said mask, said rib elements being straight, mutually parallel and successively offset laterally with end portions thereof being disposed side-by-side, said rib elements being arranged as sections of chords of said curved contour of the skirt which are oriented orthogonal to the central axis of the tube.

6. For use with a rectangular color cathode ray tube having a faceplate, a generally rectangular shadow mask comprising a sheet of electrically conductive material having a curved central portion with its convex surface facing forwardly toward the faceplate when the mask is operatively mounted in a tube and having a pattern of electron-transmissive apertures formed therein and a forwardly directed, outwardly flared electronshielding skirt of substantially constant depth surrounding said central portion and following the curved contour thereof, said skirt having formed therein strengthening rib elements, said rib elements on each side being straight, mutually parallel, orthogonal to the tube central axis, and successively offset laterally with end portions thereof disposed side-by-side, said rib elements being arranged such that as a group they follow the contour of the mask central portion.

7. In a cathode ray tube, the combination comprising: an evacuable envelope including a generally rectan gular faceplate having on an inside surface a phosphor screen; electron gun means for generating one or more beams of electrons; a generally rectangular shadow mask between said electron gun means and said faceplate, said mask having a perforate curved central portion with its convex surface facing forwardly toward the faceplate and a forwardly directed skirt flared outwardly at an angle substantially corresponding to the angle of maximum electron beam deflection surrounding said central portion for shielding said screen from stray or overscanned electrons which reflect off the inner surface of the envelope; and

a plurality of mask suspension devices, one located at each corner of the mask, coupling said mask to said envelope for supporting said mask at a predetermined spacing from said faceplate.

8. In a cathode ray tube, the combination comprising:

an evacuable envelope including a funnel and a generally rectangular, flangeless faceplate sealed to the funnel and having on an inside surface a phosphor screen;

electron gun means for generating one or more beams of electrons;

a shadow mask between said electron gun means and said faceplate, said mask being generally rectangular and torsionally flexible and having a perforate curved central portion with its convex surface facing forwardly toward the faceplate and a forwardly directed, outwardly flared skirt surrounding said central portion for shielding said screen from stray or overscanned electrons, said skirt having formed integrally therein discrete raised ribs extending along the skirt for increasing the strength of the mask; and

a plurality of mask suspension devices, one at each corner of the mask, interconnecting said mask and said faceplate for supporting said mask at a predetermined spacing from said faceplate.

9. The mask defined by claim 8 wherein said skirt is of substantially constant depth around said central portion, and has a curved contour following the curvature of said central portion of the mask, and wherein said skirt is flared at an angle corresponding to the angle of maximum electron beam deflection in the tube.

10. The mask defined by claim 9 wherein said strengthening ribs comprise rib elements extending lengthwise along at least the opposed long sides of said mask, said rib elements being straight, mutually parallel and successively offset laterally with end portions thereof being disposed side-by-side, said rib elements beingarranged as sections of chords of said curved contour of the skirt which are oriented orthogonal to the central axis of the tube.

11. In a cathode ray tube, the combination comprising:

an evacuable envelope including a funnel and a generally rectangular front panel comprising a faceplate surrounded by a rearwardly directed flange, said faceplate having on an inside surface a phosphor screen;

electron gun means for generating one or more beams of electrons;

a shadow mask between said electron gun means and said faceplate, said mask being of one-piece, generally rectangular, and torsionally flexible construction and having a perforate curved central portion with its convex surface facing forwardly toward the faceplate and a forwardly directed skirt flared outwardly at an angle substantially corresponding to the angle of maximum deflection of said beams of electrons and surrounding said central portion for shielding said screen from stray or overscanned electrons; and

a plurality of mask suspension devices, one at each corner of the mask, interconnecting said mask and said flange of said front panel for supporting said mask at a predetermined spacing from said face plate.

12. The mask defined by claim 11 wherein said skirt has formed integrally therein strengthening rib elements extending lengthwise along at least the opposed long sides of said mask, said rib elements being straight, mutually parallel and successively offset laterally with end portions thereof being disposed side-by-side, said rib elements being arranged as sections of chords of said curved contour of the skirt which are oriented orthogonal to the central axis of the tube.

13. In a cathode ray tube, the combination comprising:

an evacuable envelope including a funnel and a generally rectangular faceplate, said faceplate having on an inside surface a phosphor screen;

electron gun means for generating one or more beams of electrons;

a generally rectangular shadow mask between said electron gun means and said faceplate, said mask being torsionally flexible and having a perforate, curved central portion with its convex surface facing forwardly toward the faceplate and a forwardly directed, outwardly flared skirt surrounding said central portion on all four sides thereof for shielding said screen from stray or overscanned electrons; and

a plurality of mask suspension devices, one at each corner of the mask, interconnecting said mask and said faceplate for supporting said mask at a predetermined spacing from said faceplate, said suspension devices each comprising a mask-mounted component cooperatively engaging a faceplatemounted component, said mask-mounted component including a mounting bracket affixed to said mask and extending around a corner of the mask from one side to the next adjacent side thereof and on the outside thereof, said bracket occupying otherwise unused space above said outwardly flared skirt of said mask.

14. In a cathode ray tube, the combination comprisan evacuable envelope including a funnel and a generally rectangular flangeless faceplate having on an inside surface a phosphor screen;

electron gun means for generating a plurality of beams of electrons;

a generally rectangular shadow mask between said electron gun means and said faceplate, said mask being torsionally flexible and having a perforate curved central portion with its convex surface facing forwardly toward the faceplate and a forwardly directed skirt flared outwardly at an angle substantially corresponding to the angle of maximum deflection of said beams of electrons, said skirt surrounding said central portions on all four sides thereof for shielding said screen from stray or overscanned electrons scattered from the inner wall of said funnel; and

a plurality of mask suspension devices, one at each corner of the mask, interconnecting said mask and said faceplate for supporting said mask at a predeerwise unused space above said outwardly flared skirt of said mask, said faceplate-mounted component including a stud affixed to the screen-bearing inner surface of said faceplate but outside of said screen, said bracket having a spring affixed thereto for resiliently coupling said bracket to said stud.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION 'P n N 3 912 963 Dated October 14 19 75 Inventor(s) Stanley J. Sedivy It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 67, delete "into" and insert -intro--.

Column 4, line 44, delete "paralle" and insert -paral1el.

Column"4, line 50, delete "dividuaily" end insert dividually-.

Column 6, line 28, delete "external" and insert electron Column 7, line 63, delete "the" and insert said-.

Signed and Scaled this Twentieth Day of July 1976 [SEAL] Arrest:

RUTH C. MASON I C. MARSHALL DANN Arresting Officer Commissioner ofParenls and Trademarks 

1. For use in a rectangular color cathode ray tube having a faceplate carrying phosphor screen, a generally rectangular, frameless shadow mask having a perforate curved central portion with its convex surface facing forwardly toward the faceplate when the mask is operatively mounted in the tube, and a forwardly directed skirt surrounding said central portion and flared outwardly at an angle corresponding substantially to the angle of maximum electron beam deflection, said skirt functioning to shield the screen from stray electrons and to impart rigidity to the mask.
 2. The mask defined by claim 1 wherein said skirt is of substantially constant depth around said central portion and has a curved contour following the curvature of said central portion of the mask, and wherein said skirt has formed integrally therein discrete raised ribs extending along the skirt for imparting strength to the mask.
 3. The mask defined by claim 2 wherein said strengthening rib comprise rib elements extending lengthwise along at least the opposed long sides of said mask, said rib elements being straight, mutually parallel and successively offset laterally with end portions thereof being disposed side-by-side, said rib elements being arranged as sections of chords of said curved contour of the skirt which are oriented orthogonal to the central axis of the tube so as to substantially synthesize a load-bearing beam having an effective load-bearing depth which is greater than the depth of any individual rib element but less than the overall depth of the skirt.
 4. For use in a rectangular color cathode ray tube having a faceplate carrying a phosphor screen, a generally rectangular shadow mask formed as a unitary structure from a sheet of electrically conductive metal and having as integral parts thereof a perforate curved central portion with its convex surface facing forwardly toward the faceplate when the mask is operatively mounted in the tube, a channel portion surrounding said central portion for strengthening the mask, and a forwardly directed, outwardly flared skirt surrounding said channel portion which functions as an external shield and which imparts rigidity to the mask.
 5. The mask defined by claim 4 wherein said skirt is of substantially constant depth around the mask and has a curved contour following the contour of said central portion of the mask, and wherein said skirt has formed integrally therein strengthing rib elements extending lengthwise along at least the opposed long sides of said mask, said rib elements being straight, mutually parallel and successively offset laterally with end portions thereof being disposed side-by-side, said rib elements being arranged as sections of chords of said curved contour of the skirt which are oriented orthogonal to the central axis of the tube.
 6. For use with a rEctangular color cathode ray tube having a faceplate, a generally rectangular shadow mask comprising a sheet of electrically conductive material having a curved central portion with its convex surface facing forwardly toward the faceplate when the mask is operatively mounted in a tube and having a pattern of electron-transmissive apertures formed therein and a forwardly directed, outwardly flared electron-shielding skirt of substantially constant depth surrounding said central portion and following the curved contour thereof, said skirt having formed therein strengthening rib elements, said rib elements on each side being straight, mutually parallel, orthogonal to the tube central axis, and successively offset laterally with end portions thereof disposed side-by-side, said rib elements being arranged such that as a group they follow the contour of the mask central portion.
 7. In a cathode ray tube, the combination comprising: an evacuable envelope including a generally rectangular faceplate having on an inside surface a phosphor screen; electron gun means for generating one or more beams of electrons; a generally rectangular shadow mask between said electron gun means and said faceplate, said mask having a perforate curved central portion with its convex surface facing forwardly toward the faceplate and a forwardly directed skirt flared outwardly at an angle substantially corresponding to the angle of maximum electron beam deflection surrounding said central portion for shielding said screen from stray or overscanned electrons which reflect off the inner surface of the envelope; and a plurality of mask suspension devices, one located at each corner of the mask, coupling said mask to said envelope for supporting said mask at a predetermined spacing from said faceplate.
 8. In a cathode ray tube, the combination comprising: an evacuable envelope including a funnel and a generally rectangular, flangeless faceplate sealed to the funnel and having on an inside surface a phosphor screen; electron gun means for generating one or more beams of electrons; a shadow mask between said electron gun means and said faceplate, said mask being generally rectangular and torsionally flexible and having a perforate curved central portion with its convex surface facing forwardly toward the faceplate and a forwardly directed, outwardly flared skirt surrounding said central portion for shielding said screen from stray or overscanned electrons, said skirt having formed integrally therein discrete raised ribs extending along the skirt for increasing the strength of the mask; and a plurality of mask suspension devices, one at each corner of the mask, interconnecting said mask and said faceplate for supporting said mask at a predetermined spacing from said faceplate.
 9. The mask defined by claim 8 wherein said skirt is of substantially constant depth around said central portion, and has a curved contour following the curvature of said central portion of the mask, and wherein said skirt is flared at an angle corresponding to the angle of maximum electron beam deflection in the tube.
 10. The mask defined by claim 9 wherein said strengthening ribs comprise rib elements extending lengthwise along at least the opposed long sides of said mask, said rib elements being straight, mutually parallel and successively offset laterally with end portions thereof being disposed side-by-side, said rib elements being arranged as sections of chords of said curved contour of the skirt which are oriented orthogonal to the central axis of the tube.
 11. In a cathode ray tube, the combination comprising: an evacuable envelope including a funnel and a generally rectangular front panel comprising a faceplate surrounded by a rearwardly directed flange, said faceplate having on an inside surface a phosphor screen; electron gun means for generating one or more beams of electrons; a shadow mask between said electron gun means and said faceplate, said mask Being of one-piece, generally rectangular, and torsionally flexible construction and having a perforate curved central portion with its convex surface facing forwardly toward the faceplate and a forwardly directed skirt flared outwardly at an angle substantially corresponding to the angle of maximum deflection of said beams of electrons and surrounding said central portion for shielding said screen from stray or overscanned electrons; and a plurality of mask suspension devices, one at each corner of the mask, interconnecting said mask and said flange of said front panel for supporting said mask at a predetermined spacing from said face plate.
 12. The mask defined by claim 11 wherein said skirt has formed integrally therein strengthening rib elements extending lengthwise along at least the opposed long sides of said mask, said rib elements being straight, mutually parallel and successively offset laterally with end portions thereof being disposed side-by-side, said rib elements being arranged as sections of chords of said curved contour of the skirt which are oriented orthogonal to the central axis of the tube.
 13. In a cathode ray tube, the combination comprising: an evacuable envelope including a funnel and a generally rectangular faceplate, said faceplate having on an inside surface a phosphor screen; electron gun means for generating one or more beams of electrons; a generally rectangular shadow mask between said electron gun means and said faceplate, said mask being torsionally flexible and having a perforate, curved central portion with its convex surface facing forwardly toward the faceplate and a forwardly directed, outwardly flared skirt surrounding said central portion on all four sides thereof for shielding said screen from stray or overscanned electrons; and a plurality of mask suspension devices, one at each corner of the mask, interconnecting said mask and said faceplate for supporting said mask at a predetermined spacing from said faceplate, said suspension devices each comprising a mask-mounted component cooperatively engaging a faceplate-mounted component, said mask-mounted component including a mounting bracket affixed to said mask and extending around a corner of the mask from one side to the next adjacent side thereof and on the outside thereof, said bracket occupying otherwise unused space above said outwardly flared skirt of said mask.
 14. In a cathode ray tube, the combination comprising: an evacuable envelope including a funnel and a generally rectangular flangeless faceplate having on an inside surface a phosphor screen; electron gun means for generating a plurality of beams of electrons; a generally rectangular shadow mask between said electron gun means and said faceplate, said mask being torsionally flexible and having a perforate curved central portion with its convex surface facing forwardly toward the faceplate and a forwardly directed skirt flared outwardly at an angle substantially corresponding to the angle of maximum deflection of said beams of electrons, said skirt surrounding said central portions on all four sides thereof for shielding said screen from stray or overscanned electrons scattered from the inner wall of said funnel; and a plurality of mask suspension devices, one at each corner of the mask, interconnecting said mask and said faceplate for supporting said mask at a predetermined spacing from said faceplate, said suspension devices each comprising a mask-mounted component cooperatively engaging a faceplate-mounted component, said mask-mounted component including a mounting bracket affixed to said mask and extending around a corner of the mask from one side to the next adjacent side thereof and on the outside thereof, said bracket occupying otherwise unused space above said outwardly flared skirt of said mask, said faceplate-mounted component including a stud affixed to the screen-bearing inner surface of said faceplate but outside of said screen, said bracket having a spring affixed thereto for resiliently coupling said bracket to said stud. 